Sensory systems evolved to allow animals to receive and process information from their surroundings. To understand how sensory systems operate in any given environment, we must understand how the physical characteristics of that environment affect the available information and its propagation and reception. In a very real sense we need to look at both the medium and the message (McLuhan and Fiore 1967). Signals in the marine environment can be substantially different from those in air, and the oceanic medium itself changes the message in a number of ways.